new motor overheating

[kellydee]

Just made the maiden voyage with my new 2007 Merc 5.7 carbed.New transom assembly,new SEI drive(alpha 1 gen 2 replacement)Heres the problem.The higher the rpm's,the higher the temp.(In the water,forward)At 1200=maybe 2000 the temp is around 160,at 2500-3000,maybe 175,over 3000 and I'm hitting around 190 and the alarm is going off.As soon as I back off the throttle,cools right down.How hot before something is ruined?Was planning on going fishing in the morning.Should be safe as long as I keep my eye on the temp and back off before the alarm sounds,right?anyway,I'm thinking impeller.?It's a brand new drive and engine but sometimes,things are bad right out of the box.Any ideas? Jerry

 

[kellydee]

Re: new motor overheating

anyone know what temp the alarm sounds at?Looks like about 190 on the guage.

 

[Don S]

Re: new motor overheating

Do you have raw water cooling, or a closed cooling system. If a closed system, do you have a full or half system?

 

[kellydee]

Re: new motor overheating

Do you have raw water cooling, or a closed cooling system. If a closed system, do you have a full or half system?

Closed/Full.

 

[Don S]

Re: new motor overheating

The outdrive raw water pump is not enough for that type cooling system. Merc recommends using an engine mounted pump when using a full closed cooling system.

 

[kellydee]

Re: new motor overheating

The outdrive raw water pump is not enough for that type cooling system. Merc recommends using an engine mounted pump when using a full closed cooling system.

They also use a different ECM.I got the San Juan CC kit at time of purchase from the dealer and questioned him on that.He said it's not needed in our area with the water being as cold as what it is(I think about 54 degrees this wk)Why would they even sell a kit that dosen't work with the motor? Are you saying it's not going to work.This sucks.When ordering,I didn't specify the San Juan kit,the dealer did.Said thats what they use.How hot before I damage something?

 

[Don S]

Re: new motor overheating

http://forums.iboats.com/showthread.php?t=187326

Go to the above link, and read my replies #26 and 44

 

[kellydee]

Re: new motor overheating

OK,did a little more investigating today.Called SEI and San Juan Engineering.SEI said they have had a couple issues with the wear plate in the water pump not sitting completely over the water cavity causing it to aerate at higher rpm's.Also issues with the impellers slipping on the hubs.The guy said it shouldn't be the slipping impeller,as they are using OEM now.San Juan said the engine driven seawater pump is not required and that they have hundreds of these systems in use(with the new dry joint exhaust) around the world including warmer climates like Florida and such,with no problems.Was gonna start by pulling the lower unit and checking it out but,when I got the boat home tonight and flushed the motor I kinda checked things out.Idling on muffs at 175deg.,coolant lines felt hot by hand(feels real hot after about 5 secs or so)but,the risers feel cool.The water exiting the transom felt luke warm at best.I MIGHT take a shower at this temp on a ROASTING summer day.Pee warm MAYBE.After raising the rpm's to arount 1600,the water exiting the transom warmed to about comfy shower temp and temp guage was maybe 5 deg cooler.At idle,top of heat exchanger is hot,like the coolant lines but,the bottom and ends are COLD,like you want your beer cold.I'm not understanding.Didn't check the exchanger at higher r's(damn it)I'll do that tomorrow.With my coolant at 175,shouldnt my exchanger be hot all over?coolant lines feel hot,outlet lines feel very much cool.

 

[kellydee]

Re: new motor overheating

bump

 

[kellydee]

Re: new motor overheating

The outdrive raw water pump is not enough for that type cooling system. Merc recommends using an engine mounted pump when using a full closed cooling system.

Don,If the outdrive water pump doesn't flow enough water then ,at idle,shouldn't the water exiting the transom and the outlet lines from the exchanger to the risers be hot?If I only had a 1/2 cc system it would be,Right?Here's my thought.Impeller slipping on hub,so at idle,not pushing enough water to fill the exchanger(thus the barely warm water and cool outlet lines at idle,slight warmth is prob just eng exhaust).At higher r's(1500-2000),now getting better flow and maybe shower temp water at transom and guage is cooler(160-170).Don't think I should try any higher r's on muffs but,on the water,at over 3000 r's,would be flowing maybe a little more but,not enough to disipate the heat from those r's and fuel burning.Does this make sense?Oh ya,Should the raw water inlet line feel pressurized?It doesn't.Not even a little.Outlet lines the same.Can pinch with 2 fingers(thumb and finger). Jerry

 

[kellydee]

Re: new motor overheating

OK,NOT the impeller.The Merc dealer where I bought the engine and San Juan both say an engine driven seawater pump(or lack of)isn't the problem but can't figure out what is.I'm gonna add one and see what happens.Dealer says maybe I need to change the sending unit for the alarm because a fresh water cooled motor is gonna run warmer than a raw water cooled.Also told me to"try" a 140 thermostat.What'll that get me,an extra 3-5 minutes before overheat?What an ***.I mean if I call a merc dealer and ask for a full fresh water cooled Merc 5.7/Alpha,shouldn't he know what to sell me?Why would I be "trying"anything?Should have installed and went boating(if I was sold compatible equipment). Talked with a mechanic the other day who said he's installed a lot of San Juan kits with no probs but,recently had a new Merc 5.0 WITH an engine driven seawater pump and COULD NOT get the motor to cool properly.Even had a Merc rep come to his shop to help figure it out.After extensive conversation with San Juan and 29 hours on the job,he found the cure.Remove the San juan kit and install a merc kit.Problem solved.Of course it's about $1500 more but,who the hell cares.If it works,that's what matters.Even free is worthless if it doesn't work.Brand new motor overheating = 1 UNHAPPY CAMPER.Waaaay to much $ invested to be having that.Guess I'm venting,sorry.How about a few pointers on thru-hull fittings?Is placement important?Of all things ,this is the one I,m least comfortable with.I don't want to screw this one up.The angle on the inside of the hull is different than on the outside so, I'm sure it would be real easy to miss my target.Woulda been a little easier with the motor out I think.I'm not going there(Ihope).Also I'm TOTALLY unfamiliar with thru-hull fittings.Are there certain ones for water pick-ups?Thought I read somewhere about transom mounted pick-ups.Is this an option?while you guys try to work your way through this novel,I'm gonna go take a pic. to post.Jerry

 

[kellydee]

Re: new motor overheating

OK,NOT the impeller.The Merc dealer where I bought the engine and San Juan both say an engine driven seawater pump(or lack of)isn't the problem but can't figure out what is.I'm gonna add one and see what happens.Dealer says maybe I need to change the sending unit for the alarm because a fresh water cooled motor is gonna run warmer than a raw water cooled.Also told me to"try" a 140 thermostat.What'll that get me,an extra 3-5 minutes before overheat?What an ***.I mean if I call a merc dealer and ask for a full fresh water cooled Merc 5.7/Alpha,shouldn't he know what to sell me?Why would I be "trying"anything?Should have installed and went boating(if I was sold compatible equipment). Talked with a mechanic the other day who said he's installed a lot of San Juan kits with no probs but,recently had a new Merc 5.0 WITH an engine driven seawater pump and COULD NOT get the motor to cool properly.Even had a Merc rep come to his shop to help figure it out.After extensive conversation with San Juan and 29 hours on the job,he found the cure.Remove the San juan kit and install a merc kit.Problem solved.Of course it's about $1500 more but,who the hell cares.If it works,that's what matters.Even free is worthless if it doesn't work.Brand new motor overheating = 1 UNHAPPY CAMPER.Waaaay to much $ invested to be having that.Guess I'm venting,sorry.How about a few pointers on thru-hull fittings?Is placement important?Of all things ,this is the one I,m least comfortable with.I don't want to screw this one up.The angle on the inside of the hull is different than on the outside so, I'm sure it would be real easy to miss my target.Woulda been a little easier with the motor out I think.I'm not going there(Ihope).Also I'm TOTALLY unfamiliar with thru-hull fittings.Are there certain ones for water pick-ups?Thought I read somewhere about transom mounted pick-ups.Is this an option?while you guys try to work your way through this novel,I'm gonna go take a pic. to post.Jerry

First pic is (obviously) before motor went in.2nd is now.Is where the gatorade bottle sits a reasonable location for the thru-hull pick-up?

 

[OH3477CH]

Re: new motor overheating

Disclaimer - I am not as smart about this stuff as some of these guys, but I noticed a couple of things...

First - nice install. I like a clean engine compartment and Merc sure does spray a nice lacquer.

Second - see the nice lacquer on those wet risers? When your boat is overheating, how hot are these? If you can touch them without losing skin you probably have enough raw water.

Final conclusion from the Padawan - your t-stat is upside down.

Ok - now the Yoda's can jump my shtuff...

 

[kellydee]

Re: new motor overheating

Disclaimer - I am not as smart about this stuff as some of these guys, but I noticed a couple of things...

First - nice install. I like a clean engine compartment and Merc sure does spray a nice lacquer.

Second - see the nice lacquer on those wet risers? When your boat is overheating, how hot are these? If you can touch them without losing skin you probably have enough raw water.

Final conclusion from the Padawan - your t-stat is upside down.

Ok - now the Yoda's can jump my shtuff...

Know what?I was wondering if I might have done that.Sure hope not cuz I wouldn't be able to kick myself in the @#$ hard enough.According to my IR gun,85-90 degrees on the risers.Water out the back of the transom,about 95 degrees(at around 1600 rpm,cooler at idle but,guage at 175)

 

[OH3477CH]

Re: new motor overheating

It's easier to mess up than it looks. Look at the t-stat carefully, decide the logical way to install it, than install it the other way.

It never looks right to me when it is right.

 

[kellydee]

Re: new motor overheating

When I get home tomorrow,I'm gonna start by removing the bypass hose from the hot water heater and cabin heat to eliminate that possibillity.If no change in idle temp,will pull the stat and check.I do remember pondering that when I installed it ,as it didn't look like the one in the instructions.I'm not inclined to believe I put it in wrong but,stranger(and dumber)things have happened.

 

[kellydee]

Re: new motor overheating

Know what?I was wondering if I might have done that.Sure hope not cuz I wouldn't be able to kick myself in the @#$ hard enough.According to my IR gun,85-90 degrees on the risers.Water out the back of the transom,about 95 degrees(at around 1600 rpm,cooler at idle but,guage at 175)

Actually,I answered this question incorrectly.When it's overheating,I'm not sure how hot the risers are because it only runs really hot when cruising at over 3000 rpm's.And guess who's running the boat.Yep,me.I haven't checked that when it's running that hot,only checked on muffs in the yard.Still,I will check the other things tomorrow before buying more parts but,I'm more inclined to believe things are right. except for enough raw water.tomorrow will tell.Guess I've been avoiding dismantling things since I'de like to believe I did it right,but....guess I better check my work.

 

[kellydee]

Re: new motor overheating

Think I have good news. Saturday is gonna be a looong wait.I disconnected the hot water heater and the cabin heat today and there was absolutely NO restriction in the lines but,instead of reconnecting them,I eliminated them just to check.could not get the motor over about 160-maybe 162 degrees,on the muffs.Has idled at 175 since the 1st time I started it.The true test will come this weekend when I can put her under load.Have positive feelings about it now.I have a feeling it's gonna cool the motor fine now but,that still means I need to add the engine mounted seawater pump if I want my hot water heater and cabin heater to work.I didn't measure, but I'de say it's about 9 feet of hose to the water heater,then maybe 3-4 feet to the heater and then back to the manifold another 8-9 ft. I'll update after i can run her

 

[jakebird]

Re: new motor overheating

I too am having an overheating problem that is driving me crazy. I have a 2004 Merc 5.7L carbed engine. 1996 Alpha I Gen II. Raw water cooled. Raw water pump is in the lower drive. I just replaced the Lower drive with a Brand New Remanufactured lower drive. When I put a clear hose between the power steering cooler and the thermostat housing, large bubbles of air form when going over 3000 rpm. I cannot figure out where this air is comming from. Can anyone help?